全文获取类型
收费全文 | 1431篇 |
免费 | 94篇 |
国内免费 | 83篇 |
专业分类
电工技术 | 35篇 |
综合类 | 90篇 |
化学工业 | 94篇 |
金属工艺 | 107篇 |
机械仪表 | 112篇 |
建筑科学 | 230篇 |
矿业工程 | 78篇 |
能源动力 | 43篇 |
轻工业 | 35篇 |
水利工程 | 8篇 |
石油天然气 | 19篇 |
武器工业 | 3篇 |
无线电 | 118篇 |
一般工业技术 | 162篇 |
冶金工业 | 79篇 |
原子能技术 | 16篇 |
自动化技术 | 379篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 26篇 |
2019年 | 25篇 |
2018年 | 31篇 |
2017年 | 26篇 |
2016年 | 36篇 |
2015年 | 40篇 |
2014年 | 85篇 |
2013年 | 101篇 |
2012年 | 112篇 |
2011年 | 127篇 |
2010年 | 98篇 |
2009年 | 71篇 |
2008年 | 65篇 |
2007年 | 99篇 |
2006年 | 92篇 |
2005年 | 80篇 |
2004年 | 50篇 |
2003年 | 64篇 |
2002年 | 54篇 |
2001年 | 34篇 |
2000年 | 49篇 |
1999年 | 41篇 |
1998年 | 25篇 |
1997年 | 12篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有1608条查询结果,搜索用时 15 毫秒
1.
The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary
shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based
on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and
remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed
finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range
of modulus ratio between inclusion and matrix material. 相似文献
2.
The results of study of the effects of yttria stabilization (0–6 mol.%) on the room-temperature fracture behavior and toughening mechanisms in zirconia-reinforced MoSi2 are presented in this paper. Transformation toughening is shown to occur only in composites reinforced with zirconia particles stabilized with 2 mol.% yttria. However, the fracture toughness levels are comparable in the other composites with yttria levels between 0 and 6 mol.%. Toughening in the other composites is attributed to the combined effects of residual stress, microcrack shielding/anti-shielding and/or crack deflection. A rigorous micromechanics-based model is presented for the estimation of residual stress levels in brittle materials reinforced with phases that can transform during cooling or under stress. The model is applied successfully to the rationalization of the observed fracture and toughening phenomena. 相似文献
3.
Genetically modified starter and protective cultures 总被引:1,自引:0,他引:1
Modern approaches towards starter and protective culture improvement rely on advances in molecular biology. For most microorganisms used for food production, gene technological methods have been well developed. By recombinant DNA technology, ‘tailor-made’ starter and protective cultures may be constructed so as to combine technically desirable features. A single strain which normally would fail to accomplish a given ‘wtask’ may now be improved so as to meet a set of requirements necessary for a specific production or preservation process (e.g. wholesomeness, no off-flavour production, overproduction of bacteriocins or particular enzymes). In addition, undesirable properties (e.g. mycotoxin or antibiotic production by cheese moulds) may be eliminated by techniques such as ‘gene disruption’. 相似文献
4.
莫灿林 《浙江理工大学学报》1992,(1)
根据空间RSCR四杆机构出现特殊位置的几何特征,运用旋转变换把空间问题转换为平面问题,对实现两特殊位置运动的空间RSCR曲柄摇杆机构的图解综合法进行了探讨。 相似文献
5.
Parameters affecting the frequencies of transformation and co-transformation with synthetic oligonucleotides in yeast. 总被引:7,自引:0,他引:7
T Yamamoto R P Moerschell L P Wakem D Ferguson F Sherman 《Yeast (Chichester, England)》1992,8(11):935-948
Factors influencing the direct transformation of the yeast Saccharomyces cerevisiae with synthetic oligonucleotides were investigated by selecting for cyc1 transformants that contained at least partially functional iso-1-cytochrome c. Approximately 3 x 10(4) transformants, constituting 0.1% of the cells, were obtained by using 1 mg of oligonucleotide in the reaction mixture. Carrier, such as heterogeneous oligonucleotides, enhanced transformation frequencies. Transformation frequencies were dramatically reduced if the oligonucleotides had a large number of mismatches or had terminally located mismatches. Transformation with oligonucleotides, but not with linearized double-strand plasmid, was efficient in a rad52- strain, suggesting that the pathway for transformation with oligonucleotides is different from that with linearized double-strand plasmid. We describe a procedure of co-transformation with two oligonucleotides, one correcting the cyc1 defect of the target allele in the host strain, and the other producing a desired amino acid alteration elsewhere in the iso-1-cytochrome c molecule; approximately 20% of the transformants obtained by co-transformation contained these desired second alterations. 相似文献
6.
自制的计量装置投入使用后安全高效。介绍了其工作原理及其特点。并同以前的计量装置进行了比较。新装置不仅经济效益好,且社会效益显著,保障了矿山的正常生产。 相似文献
7.
本文阐述了氧化锆增韧陶瓷(ZTC)的相变增韧机理,并探讨了热处理工艺对ZTC的相变及显微组织的影响规律。 相似文献
8.
采用Bowman和Cole提出的有机磷分级体系,分3个灌水量对外源活性有机磷β-甘油磷酸钠在黄棕壤中的淋溶和转化特征进行了研究。结果表明,大于50mm的灌水量可以使β-甘油磷酸钠发生淋溶。施入黄棕壤中的β-甘油磷酸钠在24h内可以转化为速效磷和中活性有机磷,灌水量愈大,速效磷和中活性有机磷积累的土层也愈深。中稳性有机磷和高稳性有机磷含量没有明显变化。 相似文献
9.
基于信号样本可以重建信号频谱包络,本文提出一种简单、实用的内插方法,将此方法的有效性和FFT的优越性结合起来应用于细化频率分辨率,以适应需要获取信号较多频谱信息的应用场合。 相似文献
10.
李波涛 《数码设计:surface》2012,(8):168-170
理工类学生由于入学前很少经过系统的美术专业训练,造型基础十分薄弱,但其在毕业时,其设计能力并不比文科生艺术生要求低,甚至在当今社会中,很大一部分企业对有着理工背景的专业设计人才的要求日益迫切。如何尽快地使其在长期固化的理性思维向活泼开放的感性思维,这是一个新的领域和挑战。素描作为其学习的第一门专业基础课,其改革势在必行。 相似文献